Hi adventurers

It's my first time in a long time posting here. I want to get a complete wheel for my XT660Z 2014, on which I want to fit a 100% dirt tyre. When I go visit my friends for trail riding weekends, I can just swop the wheels out. Does anyone know what difference an 18" wheel will make to the performance? I like the idea of having a little extra ground clearance, but I'm also wondering what it will do with regards to balance, power and handling...

Any advice will be greatly appreciated